Structural determination of niobium-doped silicon clusters by far-infrared spectroscopy and theory

In this work, the structures of cationic SinNb+ (n = 4-12) clusters are determined using the combination of infrared multiple photon dissociation (IR-MPD) and density functional theory (DFT) calculations. The experimental IR-MPD spectra of the argon complexes of SinNb+ are assigned by comparison to the calculated IR spectra of low-energy structures of SinNb+ that are identified using the stochastic 'random kick' algorithm in conjunction with the BP86 GGA functional. It is found that the Nb dopant tends to bind in an apex position of the Si-n framework for n = 4-9 and in surface positions with high coordination numbers for n = 10-12. For the larger doped clusters, it is suggested that multiple isomers coexist and contribute to the experimental spectra. The structural evolution of SinNb+ clusters is similar to V-doped silicon clusters (J. Am. Chem. Soc., 2010, 132, 15589-15602), except for the largest size investigated (n = 12), since V takes an endohedral position in Si12V+. The interaction with a Nb atom, with its partially unfilled 4d orbitals leads to a significant stability enhancement of the Si-n framework as reflected, e.g. by high binding energies and large HOMO-LUMO gaps.EC/FP7/226716/EU/European Light Sources Activities - Synchrotrons and Free Electron Lasers/ELISADFG, FOR 1282, Controlling the electronic structure of semiconductor nanoparticles by doping and hybrid formatio

Does virulence assessment of Vibrio anguillarum using sea bass (Dicentrarchus labrax) larvae correspond with genotypic and phenotypic characterization?

Background: Vibriosis is one of the most ubiquitous fish diseases caused by bacteria belonging to the genus Vibrio such as Vibrio (Listonella) anguillarum. Despite a lot of research efforts, the virulence factors and mechanism of V. anguillarum are still insufficiently known, in part because of the lack of standardized virulence assays. Methodology/Principal Findings: We investigated and compared the virulence of 15 V. anguillarum strains obtained from different hosts or non-host niches using a standardized gnotobiotic bioassay with European sea bass (Dicentrarchus labrax L.) larvae as model hosts. In addition, to assess potential relationships between virulence and genotypic and phenotypic characteristics, the strains were characterized by random amplified polymorphic DNA (RAPD) and repetitive extragenic palindromic PCR (rep-PCR) analyses, as well as by phenotypic analyses using Biolog's Phenotype MicroArray (TM) technology and some virulence factor assays. Conclusions/Significance: Virulence testing revealed ten virulent and five avirulent strains. While some relation could be established between serotype, genotype and phenotype, no relation was found between virulence and genotypic or phenotypic characteristics, illustrating the complexity of V. anguillarum virulence. Moreover, the standardized gnotobiotic system used in this study has proven its strength as a model to assess and compare the virulence of different V. anguillarum strains in vivo. In this way, the bioassay contributes to the study of mechanisms underlying virulence in V. anguillarum

Interpersonal dynamics in assessment center exercises: Effects of role player portrayed disposition

Although interpersonal interactions are the mainstay of many assessment center exercises, little is known about how these interactions unfold and affect participant behavior and performance. More specifically, participants interact with role players who have been instructed to demonstrate behavior reflecting specific dispositions as part of the exercise. This study focuses on role player portrayed disposition as a potentially important social demand relevant to participant behavior and performance in interpersonal simulations. We integrate interpersonal theory and trait activation theory to formulate hypotheses about the effects of role player portrayed disposition on participant behavior and performance in 184 interpersonal simulations. A significant effect of portrayed disposition was found for participant relationship building and directive communication behavior. Furthermore, portrayed disposition moderated the relationship between participant use of these behaviors and performance ratings. Conceptually, this study sheds light on the complementary mechanisms and social demands that produce participant performance differences across exercises. At a practical level, this study provides valuable evidence-based guidance for developing interpersonal simulations

Nature of the interaction between rare gas atoms and transition metal doped silicon clusters: the role of shielding effects

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Mass spectrometry experiments show an exceptionally weak bonding between Si7Mn+ and rare gas atoms as compared to other exohedrally transition metal (TM) doped silicon clusters and other SinMn+ (n = 5-10) sizes. The Si7Mn+ cluster does not form Ar complexes and the observed fraction of Xe complexes is low. The interaction of two cluster series, SinMn+ (n = 6-10) and Si7TM+ (TM = Cr, Mn, Cu, and Zn), with Ar and Xe is investigated by density functional theory calculations. The cluster-rare gas binding is for all clusters, except Si7Mn+ and Si7Zn+, predominantly driven by short-range interaction between the TM dopant and the rare gas atoms. A high s-character electron density on the metal atoms in Si7Mn+ and Si7Zn+ shields the polarization toward the rare gas atoms and thereby hinders formation of short-range complexes. Overall, both Ar and Xe complexes are similar except that the larger polarizability of Xe leads to larger binding energies.DFG, FOR 1282, Controlling the electronic structure of semiconductor nanoparticles by doping and hybrid formatio

Pentagon, Hexagon, or Bridge? Identifying the Location of a Single Vanadium Cation on Buckminsterfullerene Surface

Buckminsterfullerene C60 has received extensive research interest ever since its discovery. In addition to its interesting intrinsic properties of exceptional stability and electron-accepting ability, the broad chemical tunability by decoration or substitution on the C60-fullerene surface makes it a fascinating molecule. However, to date there is uncertainty about the binding location of such decorations on the C60 surface, even for a single adsorbed metal atom. In this work, we report the gas-phase synthesis of the C60V+ complex and its in-situ characterization by mass spectrometry and in-frared spectroscopy with the help of quantum chemical calculations and molecular dynamics simulations. We identify the most probable binding position of a vanadium cation on C60 above a pentagon center in eta5-fashion, demonstrate a high thermal stability for this complex, and explore the bonding nature between C60 and the vanadium cation, reveal-ing that large orbital and electrostatic interactions lie at the origin of the stability of the eta5-C60V+ complex.Comment: 29 pages (11 pages for main text and 17 pages for the supporting information

A phase III randomized-controlled, single-blind trial to improve quality of life with stereotactic body radiotherapy for patients with painful bone metastases (ROBOMET)

Background Bone metastases represent an important source of morbidity in cancer patients, mostly due to severe pain. Radiotherapy is an established symptomatic treatment for painful bone metastases, however, when conventional techniques are used, the effectiveness is moderate. Stereotactic body radiotherapy (SBRT), delivering very high doses in a limited number of fractions in a highly conformal manner, could potentially be more effective and less toxic. Methods This is a phase III, randomized-controlled, single-blind, multicenter study evaluating the response rate of antalgic radiotherapy for painful bone metastases and the acute toxicity associated with this treatment. A total of 126 patients will be randomly assigned to receive either the standard schedule of a single fraction of 8.0 Gy delivered through three-dimensional conformal radiotherapy or a single fraction of 20.0 Gy delivered through SBRT. Primary endpoint is pain response at the treated site at 1 month after radiotherapy. Secondary endpoints are pain flare at 24-48-72 h after radiotherapy, duration of pain response, re-irradiation need, acute toxicity, late toxicity, quality of life and subsequent serious skeletal events. In a supplementary analysis, patient-compliance for a paper-and-pencil questionnaire will be compared with an electronic mode. Discussion If a dose-escalated approach within the context of single fraction stereotactic body radiotherapy could improve the pain response to radiotherapy and minimize acute toxicity, this would have an immediate impact on the quality of life for a large number of patients with advanced cancer. Potential disadvantages of this technique include increased pain flare or a higher incidence of radiation-induced fractures. Trial registration: The Ethics committee of the GZA Hospitals (B099201732915) approved this study on September 4th 2018. Trial registered on Clinicaltrials. gov (NCT03831243) on February 5th 2019

Controlling CO adsorption on Pt clusters by dopant-induced charge transfer

The study of small clusters, particles composed of only a few atoms, is not only interesting because of their intrinsic physical properties, strongly influenced by quantum confinement and subjected to significant size-to-size variations, but also because clusters are ideal model systems for the investigation of complex chemical reactions. In this article, we describe how doped platinum clusters composed of less than 20 atoms can be used to address questions about physical and chemical processes taking place in proton-exchange membrane fuel cells. Combining mass spectrometric experiments with theoretical calculations, the particular role of dopant-induced electronic charge transfers in the interaction of platinum nanoparticles with carbon monoxide molecules is investigated.The work in Valladolid was supported by MINECO (grant number MAT2014-54378-R)Junta de Castilla y Leon (grant number VA050U14

Spontaneous doping of two-dimensional NaCl films with Cr atoms: aggregation and electronic structure

Upon deposition of Cr atoms on ultrathin NaCl/Au(111) films they form substituting dopants either replacing Na or Cl ions, thereby changing the electronic properties of the film and in particular the work function